The 3-methyl ethers of oestrone, oestradiol and oestriol were administered intramuscularly in oil to human subjects. Demethylation to the parent oestrogens occured as shown by the recovery of considerable amounts of oestrone, oestradiol and oestriol in the urine. The relative amounts of these three oestrogens were the same in the urine as if the parent oestrogens had been administered, but the yields were less and the rate of elimination was slower.